Plasma abatement of compounds containing heavy atoms

ABSTRACT

A plasma abatement process for abating effluent containing compounds from a processing chamber is described. A plasma abatement process takes gaseous foreline effluent from a processing chamber, such as a deposition chamber, and reacts the effluent within a plasma chamber placed in the foreline path. The plasma dissociates the compounds within the effluent, converting the effluent into more benign compounds. Abating reagents may assist in the abating of the compounds. The abatement process may be a volatizing or a condensing abatement process. Representative volatilizing abating reagents include, for example, CH 4 , H 2 O, H 2 , NF 3 , SF 6 , F 2 , HCl, HF, Cl 2 , and HBr. Representative condensing abating reagents include, for example, H 2 , H 2 O, O 2 , N 2 , O 3 , CO, CO 2 , NH 3 , N 2 O, CH 4 , and combinations thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/638,871, filed on Mar. 4, 2015, now U.S. Pat. No. 9,649,592, whichapplication claims priority to U.S. Provisional Patent Application Ser.No. 61/949,160, filed on Mar. 6, 2014, and to U.S. Provisional PatentApplication Ser. No. 62/053,698, filed on Sep. 22, 2014, which areincorporated by reference herein.

BACKGROUND

Field

Embodiments of the present disclosure generally relate to abatement forsemiconductor processing equipment. More particularly, embodiments ofthe present disclosure relate to techniques for abating compoundspresent in the effluent of semiconductor processing equipment.

Description of the Related Art

Effluent produced during semiconductor manufacturing processes includesmany compounds which must be abated or treated before disposal, due toregulatory requirements and environmental and safety concerns. Amongthese compounds are perfluorocarbons (PFCs), which are used, forexample, in etching processes. Remote plasma sources (RPS) or in-lineplasma sources (IPS) have been used for abatement of PFCs and globalwarming gases. However, the design of current abatement technology forabating other gases used in semiconductor processing, such as gasescontaining heavy atoms and particulate matter generated therefrom isinadequate. Such gases and particulate matter are harmful to both humanhealth and the environment, along with being harmful to semiconductorprocessing equipment, such as processing pumps.

Accordingly, what is needed in the art is an improved abatement method.

SUMMARY

Embodiments disclosed herein include a system for abating effluent froma processing chamber. The system includes a magnetically enhanced plasmasource coupled to a foreline of a processing chamber. The processingchamber is a deposition chamber. The system also includes a reagentsource positioned upstream of the plasma source and coupled with theplasma source. The reagent source is configured to deliver an abatingreagent to the plasma source.

In one embodiment, an apparatus for abating effluent from a processingchamber is provided. The apparatus includes a plasma source coupled to aforeline of a deposition chamber, the plasma source comprising a firstplate having an outer edge and an inner edge, a second plate parallel tothe first plate, wherein the second plate has an outer edge and an inneredge, an outer wall disposed between the outer edges of the first andsecond plates, an electrode disposed between the inner edges of thefirst and second plates, a first plurality of magnets disposed on thefirst plate, and a second plurality of magnets disposed on the secondplate, and a reagent source positioned upstream of the plasma source,wherein the reagent source is coupled with the plasma source, andwherein the reagent source is configured to deliver an abating reagentto the plasma source, the abating reagent selected from the groupcomprising BCl₃, CCl₄, SiCl₄, NF₃, SF₄, SF₆, SF₈, a reducing compound, ahalogenated etching compound, CH₄, H₂, F₂, HCl, HF, Cl₂, HBr, O₂, N₂,O₃, CO, CO₂, NH₃, N₂O, CH₄, and combinations thereof.

In another embodiment, the apparatus includes a plasma source coupled toa gas line of a deposition chamber, the plasma source comprising a firstplate having an outer edge and an inner edge, a second plate parallel tothe first plate, wherein the second plate has an outer edge and an inneredge, an inner wall disposed between the inner edges of the first andsecond plates, wherein the first plate and the second plate areconcentric with the inner wall, an outer wall disposed between the outeredges of the first and second plates, the first plate, the second plate,the inner wall and the outer wall defining a plasma region, a firstplurality of magnets disposed on the first plate, and a second pluralityof magnets disposed on the second plate, and a reagent source positionedupstream of the plasma source, wherein the reagent source is coupledwith the plasma source, and wherein the reagent source is configured todeliver an abating reagent to the plasma source.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 depicts a schematic diagram of a substrate processing system inaccordance with some embodiments.

FIG. 2A is a cross sectional perspective view of the plasma sourceaccording to one embodiment.

FIG. 2B is a cross sectional bottom view of the plasma source accordingto one embodiment.

FIG. 2C is an enlarged view of a metal shield according to oneembodiment.

FIG. 3 is a flow diagram illustrating one embodiment of a method forabating effluent exiting a processing chamber.

FIG. 4 is a flow diagram illustrating one embodiment of a method forabating effluent exiting a processing chamber.

To facilitate understanding, identical reference numerals have beenused, wherever possible, to designate identical elements that are commonto the Figures. Additionally, elements of one embodiment may beadvantageously adapted for utilization in other embodiments describedherein.

DETAILED DESCRIPTION

Embodiments disclosed herein include a plasma abatement process formaterials present in an effluent exiting a processing chamber. A plasmaabatement process takes foreline effluent from a processing chamber,such as a deposition chamber, an etch chamber or other vacuum processingchamber, and reacts the effluent within a plasma chamber placed in theforeline path. The plasma energizes the materials present in theeffluent, making conversion of the material into a more benign form moreefficient. In some embodiments, the plasma may at least partiallydissociate the materials present within the effluent, which increasesthe efficiency of the conversion of the materials within the effluentinto more benign forms. An abating reagent may assist in the abating ofthe materials present within the effluent. The abatement process may bea volatilizing or a condensing abatement process.

A volatilizing abatement process converts materials, such as SiF_(x),which can form SiO₂, into gaseous species that will not form solidswithin a vacuum pump downstream of the abatement process. An abatingreagent that may be used in a volatizing abatement process is referredto herein as a volatilizing abating reagent. Representative volatilizingabating reagents include, for example, CH₄, H₂O, H₂, NF₃, SF₆, F₂, HCl,HF, Cl₂, and HBr. Representative volatilizing abating reagents alsoinclude a combination of CH_(x)F_(y) and O₂ and/or H₂O, and acombination of CF_(x) and O₂ and/or H₂O. A condensing abatement processconverts materials within the effluent into solids, and traps theconverted solids so that the solids do not reach the vacuum pump. Anabating reagent that may be used in a condensing abatement process isreferred to herein as a condensing abating reagent. Representativecondensing abating reagents include, for example, H₂, H₂O, O₂, N₂, O₃,CO, CO₂, NH₃, N₂O, CH₄, and combinations thereof.

FIG. 1 depicts a schematic diagram of a processing system 100 inaccordance with the embodiments disclosed herein. As shown in FIG. 1, aforeline 102 couples a processing chamber 101 with an abatement system111. The processing chamber 101 may be, for example, a processingchamber for carrying out a deposition process, an etching process,annealing or a cleaning process, among others. Representative chambersfor carrying out a deposition process include deposition chambers, suchas, for example, plasma enhanced chemical vapor deposition (PECVD)chambers, chemical vapor deposition (CVD) chambers, or physical vapordeposition (PVD) chambers. In some embodiments, the deposition processmay be one that deposits dielectrics, such as silicon dioxide, (SiO₂),silicon nitride (SiN_(x)), silicon oxynitride (SiON), crystallinesilicon, a-Si, doped a-Si, fluorinated glass (FSG), phosphorous dopedglass (PSG), boron-phosphorous doped glass (BPSG), carbon-doped glass,and other low-k dielectrics, such as polyimides and organosiloxanes. Inother embodiments, the deposition process may be one that depositsmetals, metal oxides, or metal nitrides, such as, for example, titanium,titanium dioxide, tungsten, tungsten nitride, tantalum, tantalumnitride, tantalum carbide, aluminum, aluminum oxide, aluminum nitride,ruthenium, or cobalt. In addition, metal alloys may be deposited, suchas lithium-phosphorous-oxynitride, lithium-cobalt, and many others.

Foreline 102 serves as a conduit that routes effluent leaving theprocessing chamber 101 to the abatement system 111. The effluent maycontain material which is undesirable for release into the atmosphere ormay damage downstream equipment, such as vacuum pumps. For example, theeffluent may contain compounds from a dielectric deposition process orfrom a metal deposition process.

Examples of materials present in the effluent that may be abated usingthe methods disclosed herein includes compounds having a heavy atom asthe central atom, or if there is no central atom, as one of the two mostcentral atoms (i.e., Si in disilane (H₃Si—SiH₃)). As used herein, a“heavy atom” includes atoms heavier than boron, such as, for example,Al, Si, W, and Ti. In some embodiments, the effluent may containcompounds wherein the heavy atoms are at least as heavy as aluminum. Inother embodiments, the effluent may contain compounds wherein the heavyatoms are at least as heavy as carbon. In other embodiments, theeffluent may contain compounds wherein the heavy atoms are at least asheavy as silicon. In some embodiments, the effluent may contain metalcompounds. In some embodiments, the effluent may not have a heavy atomas the central atom. In some embodiments, the effluent may be free orsubstantially free of fluorocarbons, such as hydrofluorocarbons (HFCs)and chlorofluorocarbons (CFCs).

Examples of silicon-containing materials present in the effluent thatmay be abated using the methods disclosed herein include, for example,silicon oxide (SiO), silicon dioxide (SiO₂), silane (SiH₄), disilane,silicon tetrachloride (SiCl₄), silicon nitride (SiN_(x)), dichlorosilane(SiH₂Cl₂), hexachlorodisilane (Si₂Cl₆), bis(t-butyl amino)silane,trisilylamine, disilylmethane, trisilylmethane, tetrasilylmethane, andtetraethyl orthosilicate (TEOS) (Si(OEt)₄). Other examples ofsilicon-containing materials include disiloxanes, such as disiloxane(SiH₃OSiH₃), trisiloxane (SiH₃OSiH₂OSiH₃), tetrasiloxane(SiH₃OSiH₂OSiH₂OSiH₃), and cyclotrisiloxane (—SiH₂OSiH₂OSiH₂O—).Examples of tungsten-containing materials present in the effluent thatmay be abated using the methods disclosed herein include, for example,W(CO)₆, WF₆, WCl₆, or WBr₆. Examples of titanium-containing materialspresent in the effluent that may be abated using the methods disclosedherein include, for example, TiCl₄ and TiBr₄. Examples ofaluminum-containing materials present in the effluent that may be abatedusing the methods disclosed herein include, for example, trimethylaluminum or triethylaluminum. Examples of other materials present in theeffluent that may be abated using the methods disclosed herein includestibine (SbH₃), germane (GH₄), hydrogen telluride, and carbon-containingcompounds, such as CH₄ and higher order alkanes.

On abatement system 111 that may be modified to benefit from theinvention is a ZFP2™ abatement system available from Applied Materials,Inc., located in Santa Clara, Calif., among other suitable systems. Asshown, the abatement system 111 includes a plasma source 104, a reagentdelivery system 106, a foreline gas injection kit 108, a controller 118,and a vacuum source 120. Foreline 102 provides effluent leaving theprocessing chamber 101 to the plasma source 104. The plasma source 104may be any plasma source coupled to the foreline 102 suitable forgenerating a plasma therein. For example, the plasma source 104 may be aremote plasma source, an in-line plasma source, or other suitable plasmasource for generating a plasma within the foreline 102 or proximate theforeline 102 for introducing reactive species into the foreline 102. Theplasma source 104 may be, for example, an inductively coupled plasmasource, a capacitively coupled plasma source, a direct current plasmasource, or a microwave plasma source. The plasma source 104 may furtherbe a magnetically enhanced plasma source of any kind described above. Inone embodiment, the plasma source 104 is a plasma source as describedwith reference to FIGS. 2A-2C.

A reagent delivery system 106 may also be coupled with the foreline 102.The reagent delivery system 106 delivers one or more reagents, such asabating reagents (which may be, for example, volatilizing or condensingabating reagents), to the foreline 102 upstream of the plasma source104. In an alternative embodiment, the reagent delivery system 106 maybe coupled directly to the plasma source 104 for delivering reagentsdirectly into the plasma source 104. The reagent delivery system 106 mayinclude a reagent source 105 (or multiple reagent sources (not shown))coupled to the foreline 102 (or the plasma source 104) via one or morevalves. For example, in some embodiments, a valve scheme may include atwo-way control valve 103, which functions as an on/off switch forcontrolling the flow the one or more reagents from the reagent source105 into the foreline 102, and a flow control device 107, which controlsthe flow rates of the one or more reagents into the foreline 102. Theflow control device 107 may be disposed between the foreline 102 and thecontrol valve 103. The control valve 103 may be any suitable controlvalve, such as a solenoid valve, pneumatic valve or the like. The flowcontrol device 107 may be any suitable active or passive flow controldevice, such as a fixed orifice, mass flow controller, needle valve orthe like.

A representative volatizing abating reagent that may be delivered by thereagent delivery system 106 includes, for example, H₂O. H₂O may be usedwhen abating effluent containing, for example, CF₄ and/or othermaterials. Another representative volatilizing reagent includes ammonia(NH₃). In other embodiments, the volatizing abating reagent may be H₂.H₂ may be used, for example, when abating effluent containing H₂O₂and/or other materials. In other embodiments, the volatilizing abatingreagent may be at least one or more of BCl₃, CCl₄, SiCl₄, NF₃, SF₄, SF₆,SF₈, other reducing or halogenated etching compounds, or combinationsthereof. Reducing or halogenated etching compounds may be used, forexample, when abating effluent containing SiH_(x), SiO, Al, CO, and/orother materials. In still other embodiments, the volatilizing abatingreagent may be a combination of CH_(x)F_(y) and O₂ and/or H₂O. Acombination of CH_(x)F_(y) and O₂ and/or H₂O may be used, for example,when abating effluent containing chlorine, TiCl₄, and/or othermaterials. In other embodiments, the volatilizing abating reagent may bea combination of CF_(x) and O₂ and/or H₂O; a combination ofC_(x)Cl_(y)F_(z) and O₂ and/or H₂O; or a combination of other freonswith O₂ and/or H₂O. A combination of CF_(x) and O₂ and/or H₂O; acombination of C_(x)Cl_(y)F_(z) and O₂ and/or H₂O; or a combination ofother freons with O₂ and/or H₂O may be used, for example, when abatingeffluent containing SiO, SiH_(x), NH_(y), NO_(x), and/or othermaterials. In other embodiments, the volatizing abating reagent may be ahalogen, such as NF₃, F₂, Cl₂, Br₂, I₂, or combinations thereof.Halogens may be used, for example, when abating effluent containingTiCl₄, trimethylamine, triethyl aluminum, and/or other materials. Inother embodiments, the volatizing abating reagent may be hydrogenhalides, such as HCl, HF, HBr, HI, or combinations thereof. Hydrogenhalides may be used, for example, when abating effluent containing SiO,SiN_(x), SiH_(y), SiO₂, and/or other materials. In other embodiments,the volatilizing abating reagent may be methane or higher order alkanes.Methane or higher order alkanes may be used, for example, when abatingeffluent containing chlorine and/or other materials. In still otherembodiments, the volatilizing abating reagent may be combinations of anynumber of any of the above-listed volatizing abating reagents. In someembodiments, the volatilizing abating reagents may be consumed by thecompounds of the effluent, and therefore, may not be consideredcatalytic.

A representative condensing abating reagent that may be delivered by thereagent delivery system 106 includes, for example, H₂O. H₂O may be usedfor example, when abating effluent containing SiH_(x), SiF_(x), CxF_(y)and/or other materials. In other embodiments, the condensing abatingreagent may be H₂. H₂ may be used, for example, when abating effluentcontaining NH_(x)F_(y), NH_(x), F_(y), F₂ (such as when used to makeammonium salts) and/or other materials. In other embodiments, thecondensing abating reagent may be O₂, N₂, O₃, CO, CO₂, NH₃, N₂O, otheroxidizers, and combinations thereof. Oxidizers may be used, for example,when abating effluent containing materials heavier than carbon. In otherembodiments, the condensing abating reagent may be alkanes, such asmethane, ethane, propane, butane, isobutane, other alkanes, orcombinations thereof. Alkanes may be used, for example, when abatingeffluent containing chlorine, aluminum, fluorine, and/or othermaterials. In still other embodiments, the condensing abating reagentsmay be combinations of any number of any of the above-listed condensingabating reagents. In some embodiments, the condensing abating reagentsmay be consumed by the compounds of the effluent, and therefore, may notbe considered catalytic.

A foreline gas injection kit 108 may also be coupled to the foreline 102upstream or downstream of the plasma source 104 (downstream depicted inFIG. 1). The foreline gas injection kit 108 may controllably provide aforeline gas, such as nitrogen (N₂), argon (Ar), or clean dry air, intothe foreline 102 to control the pressure within the foreline 102. Theforeline gas injection kit 108 may include a foreline gas source 109followed by a pressure regulator 110, further followed by a controlvalve 112, and even further followed by a flow control device 114. Thepressure regulator 110 sets the gas delivery pressure set point. Thecontrol valve 112 turns on and off the gas flow. The control valve 112may be any suitable control valve, such as discussed above for controlvalve 103. The flow control device 114 provides the flow of gasspecified by the set point of pressure regulator 110. The flow controldevice 114 may be any suitable flow control device, such as discussedabove for flow control device 107.

In some embodiments the foreline gas injection kit 108 may furtherinclude a pressure gauge 116. The pressure gauge 116 may be disposedbetween the pressure regulator 110 and the flow control device 114. Thepressure gauge 116 may be used to measure pressure in the kit 108upstream of the flow control device 114. The measured pressure at thepressure gauge 116 may be utilized by a control device, such as acontroller 118, discussed below, to set the pressure upstream of theflow control device 114 by controlling the pressure regulator 110.

In some embodiments, the control valve 112 may be controlled by thecontroller 118 to only turn gas on when the reagent from the reagentdelivery system 106 is flowing, such that usage of gas is minimized. Forexample, as illustrated by the dotted line between control valve 103 ofthe reagent delivery system 106 and the control valve 112 of the kit108, the control valve 112 may turn on (or off) in response to thecontrol valve 103 being turned on (or off).

The foreline 102 may be coupled to a vacuum source 120 or other suitablepumping apparatus. The vacuum source 120 pumps the effluent from theprocessing chamber 101 to appropriate downstream effluent handlingequipment, such as to a scrubber, incinerator or the like. In someembodiments, the vacuum source 120 may be a backing pump, such as a drymechanical pump or the like. The vacuum source 120 may have a variablepumping capacity with can be set at a desired level, for example, tocontrol or provide additional control of pressure in the foreline 102.

The controller 118 may be coupled to various components of the substrateprocessing system 100 to control the operation thereof. For example, thecontroller may monitor and/or control the foreline gas injection kit108, the reagent delivery system 106, and/or the plasma source 104 inaccordance with the teachings disclosed herein.

The embodiments of FIG. 1 are schematically represented and somecomponents have been omitted for simplicity. For example, a high speedvacuum pump, such as a turbo molecular pump or the like, may be disposedbetween the processing chamber 101 and the foreline 102 for removingeffluent gases from the processing chamber 101. Additionally, othervariants of components may be provided to supply the foreline gas, thereagent, and/or the plasma.

In embodiments of the method disclosed herein, effluent containingundesirable material exiting from the processing chamber 101 enters theplasma source 104. An abating reagent, such as a volatilizing orcondensing abating reagent, enters the plasma source 104. A plasma isgenerated from the abating reagent within the plasma source 104, therebyenergizing the abating reagent, and in some embodiments, also energizingthe effluent. In some embodiments, at least some of the abating reagentand/or material entrained in the effluent are at least partiallydisassociated. The identity of the abating reagent, the flow rate of theabating reagent, the foreline gas injection parameters, and the plasmageneration conditions may be determined based on the composition of thematerial entrained in the effluent and may be controlled by thecontroller 118. In an embodiment where the plasma source 104 is aninductively coupled plasma source, dissociation may require several kWof power.

The abating agent may include, for example, CH₄, H₂O, H₂, NF₃, SF₆, F₂,HCl, HF, Cl₂, HBr, O₂, N₂, O₃, CO, CO₂, NH₃, N₂O, CH₄, and combinationsthereof. The abating agent may also include a combination of CH_(x)F_(y)and O₂ and/or H₂O, and a combination of CF_(x) and O₂ and/or H₂O.Different abating agents may be used for treating effluent havingdifferent compositions.

FIG. 2A is a cross sectional perspective view of the plasma source 104according to one embodiment. As shown in FIG. 2A, the body 200 mayinclude an outer wall 204, an inner wall 206, a first plate 203 and asecond plate 205. The first plate 203 and the second plate 205 may havea ring shape and the outer and inner walls 204, 206 may be cylindrical.The inner wall 206 may be a hollow electrode which may be coupled to anRF source (not shown). The outer wall 204 may be grounded. The firstplate 203 and the second plate 205 may be concentric with the inner wall206. The first plate 203 may have an outer edge 207 and an inner edge209 and the second plate 205 may have an outer edge 211 and an inneredge 213. The outer wall 204 may have a first end 212 and a second end214, and the inner wall 206 may have a first end 216 and a second end218. A first insulating ring 230 may be disposed adjacent to the firstend 216 of the inner wall 206 and a second insulating ring 232 may bedisposed adjacent to the second end 218 of the inner wall 206. Theinsulating rings 230, 232 may be made of an insulating ceramic material.The outer edge 207 of the first plate 203 may be adjacent to the firstend 212 of the outer wall 204 and the outer edge 211 of the second plate205 may be adjacent to the second end 214 of the outer wall 204. In oneembodiment, the ends 212, 214 of the outer wall 204 are in contact withthe outer edges 207, 211, respectively. The inner edge 209 of the firstplate 203 may be adjacent to the first insulating ring 230 and the inneredge 213 of the second plate 205 may be adjacent to the secondinsulating ring 232. The plasma region 284 is defined between the outerwall 204 and the inner wall 206 and between the first plate 203 and thesecond plate 205, and a capacitively coupled plasma may be formed in theplasma region 284.

In order to keep the inner wall 206 cool during operation, a coolingjacket 220 may be coupled to the inner wall 206. The inner wall 206 mayhave a first surface 242 facing the outer wall 204 and a second surface244 opposite the first surface. In one embodiment, both surfaces 242,244 are linear and the cooling jacket 220 is coupled to the secondsurface 244. In one embodiment, the first surface 242 is curved and thesecond surface 244 is linear, as shown in FIG. 2B. The cooling jacket220 may have a cooling channel 208 formed therein, and the coolingchannel 208 is coupled to a coolant inlet 217 and a coolant outlet 219for flowing a coolant, such as water, into and out of the cooling jacket220. A first plurality of magnets 210 may be disposed on the first plate203. In one embodiment, the first plurality of magnets 210 may be amagnetron having an array of magnets and may have an annular shape. Asecond plurality of magnets 240 may be disposed on the second plate 205,and the second plurality of magnets 240 may be a magnetron having anarray of magnets and may have the same shape as the first plurality ofmagnets 210. In one embodiment, the second plurality of magnets 240 is amagnetron and has an annular shape. In one embodiment, the magnets 210,240 are linear arrays formed near the ends 270, 272. The magnets 210,240 may have opposite polarity facing the plasma region 284. The magnets210, 240 may be rare-earth magnets, such as neodymium ceramic magnets.One or more gas injection ports may be formed on the first plate 203 orfirst and second plates 203, 205, for injecting the abating agent and/ora purging gas. The purge gas may reduce deposition on shields 250, 252(shown in FIG. 2B).

FIG. 2B is a cross sectional bottom view of the plasma source 104according to one embodiment. As shown in FIG. 2B, the first surface 242of the inner wall 206 has a plurality of groves 246 disposed thereon.The groves 246 may be a continuous trench. Even though the first surface242 shown in FIG. 2B is curved, the groves 246 may be formed on thelinear first surface 242, as shown in FIG. 2A. During operation, theinner wall 206 is powered by a radio frequency (RF) power source and theouter wall 204 is grounded, forming an oscillating or constant electricfield “E” in the plasma region 284, depending on the type of appliedpower, RF or direct current (DC), or some frequency in between. Bi-polarDC and bi-polar pulsing DC power may also be used with inner and outerwalls forming the two opposing electrical poles. The magnets 210, 240create a largely uniform magnetic field “B” that is substantiallyperpendicular to the electric field “E.” In this configuration, aresulting force causes the current that would normally follow theelectric field “E” to curve towards the second end 272 (out of thepaper), and this force raises the plasma density significantly bylimiting plasma electron losses to the grounded wall. In the case ofapplied RF power, this would result in an annular oscillating currentdirected largely away from the grounded wall. In the case of applied DCpower, this would result in a constant annular current directed largelyaway from the grounded wall. This effect of current divergence from theapplied electric field is known as the “Hall effect.” The plasma formedin the plasma region 284 dissociates at least a portion of theby-products in the effluent flowing in from the opening 280 at the firstend 270 to the opening 282 at the second end 272. Abating agent may bealso injected to react with the dissociated and forming less hazardouscompounds. In one embodiment, the effluent contains silane, and theabating agent may be water or oxygen, which turns silane in the effluentinto glass.

A first metal shield 250 may be disposed inside the plasma region 284adjacent to the first plate 203, a second metal shield 252 may bedisposed inside the plasma region 284 adjacent to the second plate 205,and a third metal shield 259 may be disposed in the plasma regionadjacent to the outer wall 204. Shields 250, 252, 259 may be removable,replaceable and/or reusable since materials may be deposited thereon.The first metal shield 250 and the second metal shield 252 may havesimilar configuration. In one embodiment, both the first metal shield250 and the second metal shield 252 have an annular shape. The firstmetal shield 250 and the second metal shield 252 each includes a stackof metal plates 254 a-254 e that are mutually isolated from one another.One or more gaps 276 (shown in FIG. 2A) may be formed in each metalplate 254 a-254 e for allowing expansion without deforming the metalplates 254 a-254 e.

FIG. 2C is an enlarged view of the metal shield 250 according to oneembodiment. For the purpose of clarity some components of the plasmasource 104 are omitted, such as the one or more gas injection ports.Each plate 254 a-254 e may be annular and have an inner edge 256 and anouter edge 258. The metal plates 254 a-254 e may be coated to changeshield surface emissivity via anodization to improve chemicalresistance, radiant heat transfer, and stress reduction. In oneembodiment, the metal plates 254 a-254 e are coated with black coloraluminum oxide. An inner portion 274 of the metal plate 254 a may bemade of a ceramic material for arcing prevention and dimensionalstability. The ends 256 of the plates 254 a-254 e are separated from oneanother by an insulating washer 260, so the plates 254 a-254 e aremutually isolated from one another. The washer 260 also separates theplate 254 e from the first plate 203. The stack of metal plates 254a-254 e may be secured by one or more ceramic rods or spacers (notshown). The one or more ceramic rods may go through the stack of metalplates 254 a-254 e and the washers, and one end of each rod is coupledto the inner wall 206 while the other end of each rod is coupled to thefirst/second plate 203, 205.

In one embodiment, the distance “D1” between the inner edge 256 and theouter edge 258 of the plate 254 a is smaller than the distance “D2”between the inner edge 256 and the outer edge 258 of the plate 254 b,which is smaller than the distance “D3” between the inner edge 256 andthe outer edge 258 of the plate 254 c, which is smaller than thedistance “D4” between the inner edge 256 and the outer edge 258 of theplate 254 d, which is smaller than the distance “D5” between the inneredge 256 and the outer edge 258 of the plate 254 e. In other words, thedistance between the inner edge 256 and the outer edge 258 is related tothe location of the plate, i.e., the further the plate is disposed fromthe plasma region 284, the greater distance between the inner edge 256and the outer edge 258. In this configuration, the electrical voltagebetween the inner wall 206 and the outer wall 204 is divided by six,since there are six gaps: between the inner wall 206 and the outer edge258 of the plate 254 a, between the outer edge 258 of the plate 254 aand the outer edge 258 of the plate 254 b, between the outer edge 258 ofthe plate 254 b and the outer edge 258 of the plate 254 c, between theouter edge 258 of the plate 254 c and the outer edge 258 of the plate254 d, between the outer edge 258 of the plate 254 d and the outer edge258 of the plate 254 e, and between the outer edge 258 of the plate 254e and the outer wall 204. Each gap has a small electric potential so theelectric field across the gap is small, such the area cannot light upand take the applied power, thus forcing the power to go into the plasmaregion 284, creating a plasma in the plasma region 284. Without theshields 250, 252 as described above, there could be a localized plasmadischarge between the first end 216 of the inner wall 206 and the firstend 212 of the outer wall 204 and between the second end 218 of theinner wall 206 and the second end 214 of the outer wall 204, and theplasma region 284 may not be filled with plasma.

The spaces between the metal plates 254 a-254 e may be dark spaces,which may be bridged with materials deposited on the plates, causing theplates to be shorted out to each other. To prevent this from happening,in one embodiment, each metal plate 254 a-254 e includes a step 262 sothe outer edge 258 of each metal plate 254 a-254 e is further away fromthe adjacent plate. The step 262 causes the outer edge 258 to benon-linear with the inner edge 256. Each step 262 shields the dark space264 formed between adjacent metal plates, so no material may bedeposited in the dark space 264.

The outer wall 204, the inner wall 206, and the shields 250, 252, 259may be all made of metal since metal is resistant to most chemistriesused in the semiconductor processes. The type of metal used may bedepending on the chemistry used in the vacuum processing chamberupstream of the plasma source 104. In one embodiment, a chlorine basedchemistry is used and the metal may be stainless steel, such as 316stainless steel. The insulating rings 230, 232 in chlorine basedchemistry may be made of quartz. In another embodiment, a fluorine basedchemistry is used and the metal may be aluminum and the insulating rings230, 232 may be made of alumina. The inner wall 206 may be made ofanodized aluminum or spray coated aluminum.

FIG. 3 is a flow diagram illustrating one embodiment of a volatilizingmethod 300 for abating effluent exiting a processing chamber. The method300 begins at block 302 by flowing effluent from a processing chamber,such as processing chamber 101, into a plasma source, such as plasmasource 104. At block 304, a volatilizing abating reagent is flowed intothe plasma source. At block 306, a plasma is generated from thevolatilizing abating reagent within the plasma source, therebyenergizing the abating reagent, and in some embodiments, also energizingthe effluent. In some embodiments, at least some of the abating reagentand/or material entrained in the effluent are at least partiallydisassociated. The material in the effluent is converted to a differentmaterial in the presence of the plasma formed in the plasma source. Thematerial in the effluent may then exit the plasma source and flow intothe vacuum source, such as vacuum source 120, and/or be further treated.

In a representative volatizing abatement process using methane, methanefrom the reagent delivery system 106 is flowed into the plasma source104. Effluent containing materials desired for abatement, such as Si, W,and Ti-containing compounds, is also flowed into the plasma source 104.A plasma is generated within the plasma source 104, and therebyconverting the Si, W, and Ti-containing compounds into methylatedcompounds. The methylated compounds are volatile and more benign tohuman health and downstream effluent handling components than theunabated effluent. For example, exposure of effluent containing SiO₂ tothe plasma results in the addition of four CH₃ groups to SiO₂, resultingin the production of tetramethylsilane (TMS), which can be pumped out toatmospheric pressure for further treatment. Similarly,tungstenhexafluoride present in the effluent can be methylated to form amethylated tungsten species, such as, for example, hexamethyltungsten.Methylating tungsten prevents the buildup of WF₆ and its by-products inpumps and vacuum lines. Likewise, titanium compounds within the effluentcan be methylated to form, for example, methyltitanium trichloride,which is volatile and will not damage vacuum pumps.

In a representative volatizing abatement process using SF₆, SF₆ from thereagent delivery system 106 may be flowed into the plasma source 104.Effluent containing materials desired for abatement, such as silane(SiH₄), is also flowed into the plasma source 104. A plasma is generatedwithin the plasma source 104 and thereby converts the silane to SiF₄,which is much more benign than the pyrophoric silane, thereby greatlyimproving effluent handling safety and reducing associated costs.

FIG. 4 is a flow diagram illustrating one embodiment of a condensingmethod 400 for abating effluent exiting a processing chamber. The method400 begins at block 402 by flowing effluent from a processing chamber,such as processing chamber 101, into a plasma source, such as plasmasource 104. At block 404, a condensing abating reagent is flowed intothe plasma source. At block 406, a plasma is generated from thecondensing abating reagent within the plasma source, thereby energizingthe abating reagent, and in some embodiments, also energizing theeffluent. In some embodiments, at least some of the abating reagentand/or material entrained in the effluent are at least partiallydisassociated. The material in the effluent is converted to a differentmaterial in the presence of the plasma formed in the plasma source. Thematerial in the effluent may then exit the plasma source and flow intothe vacuum source, such as vacuum source 120, and/or be further treated.At optional block 406, the particulate matter or deposited material maybe removed from the plasma source.

In a representative condensing abatement process using oxygen, oxygenfrom the reagent delivery system 106 is flowed into the plasma source104. Effluent containing materials desired for abatement, such as silane(SiH₄) is also flowed into the plasma source 104. A plasma is generatedwithin the plasma source 104 and thereby converts the silane to SiO₂glass. The SiO₂ glass, which may be trapped or otherwise collected inthe plasma source, is much more benign than the pyrophoric silane,thereby greatly improving effluent handling safety and reducingassociated costs.

In other embodiments, condensing abating reagents and volatilizingabating reagents may be used in succession. For example, a chamber mayproduce effluent containing SiH_(x) and O₂. When energized with aplasma, SiH_(x) and O₂ tend to form a glassy SiO₂ material in acondensing abatement process. A subsequent process in the processingchamber may use, for example, NF₃, which decomposes into NF_(x) andatomic fluorine (F₂). Some of the F₂ may be consumed in the processingchamber, but some of the F₂ may be evacuated unused. The unused F₂ maybe used by the abatement system 111 to remove the condensed glassy SiO₂material in a volatilizing abatement process. The volatizing abatementprocess may be performed by using additional volatilizing abatementreagents or by using only the F₂ from the effluent. Thus, in a two-parttreatment process, the foreline abatement process can make efficient useof all effluent, as well as rendering the effluent safer when broughtfrom vacuum to atmospheric pressure by the system pump. In otherembodiments, a volatizing abating reagent may be used first and acondensing abating reagent may be used thereafter.

The previously described embodiments have many advantages. For example,the techniques disclosed herein can convert volatile, toxic, and/orexplosive effluent into much more benign chemicals that can be moresafely handled. The plasma abatement process is beneficial to humanhealth in terms of acute exposure to the effluent by workers and byconversion of pyrophoric or toxic materials into more environmentallyfriendly and stable materials. The plasma abatement process alsoprotects semiconductor processing equipment, such as, for example,vacuum pumps, from excessive wear and premature failure by removingparticulates and/or other corrosive materials from the effluent stream.Moreover, performing the abatement technique on the vacuum foreline addsadditional safety to workers and equipment. If an equipment leak occursduring the abatement process, the low pressure of the effluent relativeto the outside environment prevents the effluent from escaping theabatement equipment. Additionally, many of the abating reagentsdisclosed herein are low-cost and versatile. For example, methane isinexpensive and can also methylate and thereby volatilize a wide arrayof metalorganic compounds. SF₆ is likewise versatile and low-cost. Theaforementioned advantages are illustrative and not limiting. It is notnecessary for all embodiments to have all the advantages.

While the foregoing is directed to embodiments of the disclosed devices,methods and systems, other and further embodiments of the discloseddevices, methods and systems may be devised without departing from thebasic scope thereof, and the scope thereof is determined by the claimsthat follow.

What is claimed is:
 1. An apparatus for abating effluent from aprocessing chamber, comprising: a plasma source coupled to a gas line ofa deposition chamber, the plasma source comprising: a first plate havingan outer edge and an inner edge; a second plate parallel to the firstplate, wherein the second plate has an outer edge and an inner edge; aninner wall disposed between the inner edges of the first and secondplates, wherein the first plate and the second plate are concentric withthe inner wall; an outer wall disposed between the outer edges of thefirst and second plates, the first plate, the second plate, the innerwall and the outer wall defining a plasma region; a first plurality ofmagnets disposed on the first plate; and a second plurality of magnetsdisposed on the second plate; and a reagent source positioned upstreamof the plasma source, wherein the reagent source is coupled with theplasma source, and wherein the reagent source is operable to deliver anabating reagent to the plasma source.
 2. The apparatus of claim 1,wherein the inner wall is a hollow electrode coupling to an RF source.3. The apparatus of claim 1, wherein the outer wall is grounded.
 4. Theapparatus of claim 1, further comprising: a first insulating ringdisposed adjacent to a first end of the inner wall; and a secondinsulating ring disposed adjacent to a second end of the inner wall,wherein the first end is opposed to the second end.
 5. The apparatus ofclaim 1, further comprising: a cooling plate coupled to the inner wall,the cooling plate has a cooling channel formed therein.
 6. The apparatusof claim 1, wherein the inner wall has a first surface facing the outerwall and a second surface opposite the first surface, wherein the firstsurface is curved and the second surface is linear.
 7. The apparatus ofclaim 6, wherein the first surface of the inner wall has a plurality ofgroves disposed thereon.
 8. The apparatus of claim 7, wherein each ofthe groves is a continuous trench.
 9. The apparatus of claim 1, whereinthe abating reagent is selected from the group comprising BCl₃, CCl₄,SiCl₄, NF₃, SF₄, SF₆, SF₈, a reducing compound, a halogenated etchingcompound, CH₄, H₂, F₂, HCl, HF, Cl₂, HBr, O₂, N₂, O₃, CO, CO₂, NH₃, N₂O,CH₄, and combinations thereof.
 10. The apparatus of claim 9, wherein theabating reagent is CH₄.
 11. The apparatus of claim 9, wherein theabating reagent is SF₆.
 12. An apparatus for abating effluent from aprocessing chamber, comprising: a plasma source coupled to a gas line ofa deposition chamber, the plasma source comprising: a first plate havingan outer edge and an inner edge; a second plate parallel to the firstplate, wherein the second plate has an outer edge and an inner edge; aninner wall disposed between the inner edges of the first and secondplates, wherein the first plate and the second plate are concentric withthe inner wall; an outer wall disposed between the outer edges of thefirst and second plates, the first plate, the second plate, the innerwall and the outer wall defining a plasma region therein; a first magnetdisposed on the first plate; and a second magnet disposed on the secondplate; and a reagent source positioned upstream of the plasma source,wherein the reagent source is coupled with the plasma source, andwherein the reagent source is operable to deliver an abating reagent tothe plasma source.